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Biomedical subjects

C T Chang

Publications and source records attributed to C T Chang.

At least 73 records · Page 4Linked to original sources
PubMed1993

Purification and some properties of peroxidase isozymes from pineapple stem.

The enzyme peroxidase is widely distributed among the higher plants. Isozymes of peroxidase are known to occur in a variety of tissues in a large number of plant species. In this study, peroxidase isozymes were purified from the extract of pineapple stem through successive steps of ammonium sulfate fractionation, CM-Sepharose CL-6B chromatographies and DEAE-Sepharose CL-6B chromatographies. By these steps, twelve isozymes of peroxidase were obtained. Some properties of the isozymes were studied and compared.

Ammonium Sulfate↗
PubMed1992

Flavonoid potentiation of contractile responses in rat blood vessels.

Certain bioflavonoids and phenolic compounds have long been known to enhance catecholamine responses, in vivo and in vitro. In the present studies the flavone, baicalein, potentiated nerve-stimulated contractions in vitro in rat tail and femoral artery isometric ring preparations. Inhibition of catecholamine reuptake with cocaine or catecholamine metabolism with tropolone and parglyine (monoamine oxidase and catecholamine-O-methyl transferase inhibitors, respectively) did not alter baicalein's ability to potentiate contractile responses to nerve stimulation. Baicalein (10(-5) M), the prototype flavone, also increased sensitivity to exogenous norepinephrine, serotonin, arginine vasopressin and to the noncatecholamine alpha-1 and alpha-2 adrenergic agonists, cirazoline and tramazoline. Structure-function studies indicated that flavone potentiation required three contiguous A or B ring hydroxylations. Several nonflavone phenol derivatives with three contiguous hydroxyls also potentiated nerve stimulation responses. As baicalein is a potent lipoxygenase inhibitor, comparisons were made between potentiating ability and lipoxygenase inhibitory activity in a series of flavonoids. There was no direct correlation between inhibition of 12-hydroxy-5,8,10,14-eicosatetraenoic acid levels in thrombin stimulated human platelets and potentiation of contractile responses in the femoral artery. Additionally, the specific substrate analog lipoxygenase inhibitor, 5,8,11-eicosatriynoic acid, and the cyclooxygenase inhibitor, ibuprofen, were nonpotentiating. Ibuprofen pretreatment did not alter the potentiating action of baicalein. It is concluded that flavonoids with three contiguous hydroxyls on either the A or B ring increase in vitro vascular responsiveness via a post-synaptic process, independent of cyclooxygenase, lipoxygenase, monoamine oxidase or catecholamine-O-methyl transferase activity.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1992

Purification and properties of chitinase from cabbage.

Chitinase has been purified from the extract of cabbage through successive steps of ammonium sulfate fractionation, chromatofocusing and Sephadex G-75 gel filtration. By these steps, the purity of the enzyme increased by 93.3 fold and the recovery of the enzyme activity was 20%. The purified enzyme had an optimal pH of 5.0, an optimal temperature between 40 to 50 degrees C and a Km of 76 microM for hydrolysis of ethylene glycol chitin. The molecular weight of the enzyme determined from filtration through Sephadex G-75 was 30,000 daltons. Heavy metal ions, Hg2+ (0.5 mM) and Ag+(2.5 mM) significantly inhibited the activity of the enzyme. NBSI1 (1.0 mM), DNFB (0.5 mM) and PMSF (0.5 mM) completely inhibited the activity of the enzyme. The enzyme also showed muramidase activity for hydrolysis of Micrococcus lysodeikticus cell wall. The presence of chitinase in cabbage may function as a defense enzyme against potential pathogens.

Ammonium Sulfate↗
PubMed1989

The inhibition of prostaglandin E1-induced corneal neovascularization by steroid eye drops.

The antiangiogenic activity of several steroid eye drops was evaluated in a PGE-induced corneal neovascularization. Pred-Forte (1% prednisolone acetate) and Maxidex (0.1% dexamethasone) were very effective in preventing neovascularization. Medroxyprogesterone acetate at 0.1% in Tears Naturale was moderately effective and fluorometholone was less effective in blocking neovascularization. Cortisone alone was not very effective; however, the addition of heparin greatly enhanced its inhibitory effect. PGE1 induced corneal neovascularization and increased the leukocytes infiltration. The application of Maxidex right after the implantation of PGE1 pellet not only inhibited the leukocytes infiltration, but also blocked the neovascularization. These results suggested that the leukocytes infiltration might be one of the factors contributing to the development of neovascularization. The effect of steroid eye drops on the growth of preformed capillaries was also evaluated. The result demonstrated that Pred-Forte also suppressed the growth of well-developed capillaries.

Alprostadil↗
PubMed1989

A procedure for purifying jack bean urease for clinical use.

Urease with a purity meeting the requirements of analytical use was purified from jack bean meal through steps consisting of 20% acetone extraction, heat treatment, acid precipitation, and lyophilization. For extraction of urease, one part of bean meal was mixed with 5 parts of 20% acetone containing 1 mM EDTA and 1 mM 2-mercaptoethanol, and stirred at 20 degrees C for 5 min. Milky substances in the extract were removed by heat treatment. Urease in the clear yellow supernatant was precipitated by adjusting the pH of the solution to 5.4 with citric acid. The acid precipitated urease was neutralized by dissolving in 0.015 M phosphate buffer, pH 8.5 (final pH 6.8 to 7.0) and then lyophilized. By this procedure, the purity of the enzyme was increase 14.7 fold, the recovery of activity was 63%, and the yield was 6.75 g from 1 kg of bean seeds. The specific activity of the preparation was 411 units/mg protein (240 units/mg solid), and the free ammonia content was less than 0.01 microgram per unit. Some other proteins were present in the urease preparation as examined by gel filtration and gradient polyacrylamide gel electrophoresis. The molecular weight of the enzyme estimated by gel filtration was 480,000. However, two urease activity bands with molecular weight of 230,000 and 480,000 were observed in the polyacrylamide gel electrophoregram. From the result of determination of blood urea nitrogen (BUN), this simple purification procedure could be used for practical preparation of urease from jack bean meal for clinical analysis.

Acetone↗
PubMed1986

Bone disease induced by anticonvulsant therapy and treatment with calcitriol (1,25-dihydroxyvitamin D3).

To evaluate the effects of calcitriol (1,25-dihydroxyvitamin D3) therapy for the bone disease induced by long-term treatment with anticonvulsants, we reviewed the medical records of 330 institutionalized oligophrenic children and young adults under 26 years of age to identify the 144 children who required anticonvulsant therapy. Of this latter group, 52 children were found to have serum alkaline phosphatase levels elevated more than 2 SDs above normal and were enrolled into this prospective three-year study. To achieve rapid resolution of the bone disease, we elected to use calcitriol at 0.25 to 0.75 micrograms/d. After 1195 patient-months of treatment, our data suggest that the dystrophic process was reversed in 42.3% of the cases, as judged by decreases in serum alkaline phosphatase levels at six months, 65.4% of cases at 12 months, and 83.3% of cases at 13 to 18 months. By 30 months of follow-up, all patients showed significant lowering of serum alkaline phosphatase levels. The improvements were slow and gradual. Twenty-six patients in the treatment series of 52 patients initially showed signs of rickets or osteomalacia on roentgenograms of the wrists. Of these 26 patients, 12 (46%) showed improvement on roentgenograms within 24 months of the beginning of treatment. With reference to complications, hypercalcemia (calcium level, greater than 11 mg/dL [2.74 mmol/L]) was encountered at the rate of one episode per 44 patient-months of treatment. Our results strongly suggest that calcitriol is effective in healing anticonvulsant-related osteomalacia among children and youths, with a low incidence of complications.

Acid Phosphatase↗
PubMed1985

Preparation of pancreatin and purification of lipase from hog pancreas.

Pancreatin containing high activities of proteolytic enzymes, amylase and lipase was prepared from optimally autolyzed hog pancreas. About one hundred grams of pancreatin were obtained from one kilogram of hog pancreas. Lipase was purified from the pancreatin preparation through steps of mild alkaline solution extraction, removing proteolytic enzymes by affinity adsorption, first ammonium sulfate fractionation, Sephacryl S-200 gel filtration, and secondary ammonium sulfate fractionation. By these steps, the purity of the enzyme increased 14 fold and the recovery of the enzyme activity was 33%. The purified lipase was not homogeneous and contained several contaminating proteins when examined by disc polyacrylamide gel electrophoresis.

Amylases↗
PubMed1984

The effects of polycations on vascular permeability in the rat. A proposed role for charge sites.

This study investigated whether charge sites in the walls of the microvasculature may play a role in maintaining the impermeability of the nonrenal capillaries to albumin. All experiments were performed in nephrectomized rats, studied in the awake state. The intravenous injection of protamine sulfate (4 mg/100 g body wt dissolved in 0.9% saline) was followed by a mean increase of 29.1% in hematocrit and a decrease of 28.4% in plasma albumin concentration over a 10-min period, indicating a significant 50-60% loss of albumin from the vascular space; a finding confirmed by studies using exogenous 125I-labeled albumin. Changes persisted for the remaining 80 min of observation, and could be reproduced by the injection of two other polycations, hexadimethrine and poly-l-lysine. These effects were not prevented by the antihistamine diphenhydramine hydrochloride. In contrast to 125I-labeled albumin, 14C-labeled neutral dextran of comparable size was not confined to the vascular space; its apparent volume of distribution progressively increased during the 90 min of observation. Intravenous injection of protamine sulfate was followed by a significantly smaller loss of 14C-dextran (36.5%) than albumin (59.1%) from the vascular space (P less than 0.01). Protamine sulfate could not be demonstrated to result in any changes in the physicochemical characteristics of albumin. These observations suggest that the negative charge sites present in nonglomerular capillary walls have functions similar to equivalent sites present in the glomerular capillaries. Thus, charge sites could contribute to the low permeability of the microvasculature to negatively charged macromolecules such as albumin. This may be an important mechanism for retaining albumin in the vascular space and preventing edema formation in health.

Animals↗
PubMed1983

5-p-benzoquinonyl-2'-deoxyuridine 5'-phosphate: a possible mechanism-based inhibitor of thymidylate synthetase.

The title compound (1), designed as a suicide inhibitor of thymidylate synthetase, can be prepared by silver(II) oxide oxidative demethylation of the corresponding dimethoxyphenyl derivative. Compound 1 shows time-dependent inactivation of thymidylate synthetase (methotrexate-resistant Lactobacillus casei) and saturation kinetics, and the inactivation is responsive to substrate protection. The inactivation is not reversible on prolonged dialysis in attempts to remove the inhibitor. The rate constant for inactivation is 0.065 s-1; the dissociation constant (Ki) was estimated to be 2 microM. The kinetics of this inactivation are compared to inactivation caused by model thiol reagents that do not have affinity for the active site of thymidylate synthetase.

Deoxyuracil Nucleotides↗
PubMed1981

Effect of CSF on bacterial growth.

The growth patterns of five potentially pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, group B beta-hemolytic streptococcus, and Klebsiella pneumoniae) and a commonly encountered, nonpathogenic microorganism (S epidermidis) were compared using CSF, trypticase soy broth (TSB), and a phosphate buffer. Each grew less in CSF than in TSB. Escherichia coli was least affected with a median difference of 2 logarithms between CSF and TSB at 24 hours of growth, whereas S epidermidis was markedly inhibited, with a median difference of 6.85 logarithms. The differences among the remaining four organisms ranged from 3.86 to 5.94 logarithms, all significantly greater than that for E. coli. Similar results were obtained at 48 hours of growth. The non-support of bacterial growth by CSF may constitute a host defense mechanism. The basis of these observations may be the presence of inhibitors or the absence of nutrients required for bacterial growth in the CSF.

Bacteria↗
PubMed1980

Hydrophobic chromatography of beta-galactosidase.

The hydrophobic interaction of beta-galactosidase with Sepharose 4B substituted with 3,3'-diaminodipropylamine was studied in both batch and column experiments. The equilibrium and the binding rate constants were determined for different phosphate buffer concentrations. The equilibrium constants exhibit a hysteresis effect, i.e., desorption constants are less than adsorption constants, and the higher the ionic strength to start the desorption, the larger the effect. The rate data are not satisfactorily described by a simple reversible first-order model. The column chromatographic data are semiquantitatively described by a local equilibrium theory without axial dispersion or intraparticle diffusion.

Adsorption↗
PubMed1980

Synthesis of 5-[(methylthio)methyl]-2'-deoxyuridine, the corresponding sulfoxide and sulfone, and their 5'-phosphates: antiviral effects and thymidylate synthetase inhibition.

Substitution on the alpha position of thymidine with methylthio (3) and methylsulfonyl (5) groups gave antiviral agents that were specific and relatively nontoxic inhibitors of herpes simplex virus replication in cell culture. The thioether (3) was effective against both types 1 and 2 of herpes simplex virus, whereas the activity of the sulfone derivative (5) was restricted to herpes simplex virus type 1. The sulfoxide derivative 1-(2-deoxy-beta-D-ribofuranosyl)-alpha-(methylsulfinyl)thymine (4) was inactive as an antiviral agent. The 5'-phosphates of these three thymidine derivatives were relatively potent inhibitors of thymidylate synthetase (Ki values range from 7.8 to 1.9 microM). It is improbable that the inhibition of this enzyme accounts for the anti-herpes activity of compounds 3 and 5.

Animals↗
PubMed1980

Oxime and dithiolane derivatives of 5-formyl-2'-deoxyuridine and their 5'-phosphates: antiviral effects and thymidylate synthetase inhibition.

5-Formyl-2'-deoxyuridine (2a), an effective inhibitor of herpes simplex virus type 1 or 2 (HSV-1, HSV-2) and vaccinia virus, was converted to the oxime (3a) and dithiolane (4a) derivatives. The oxime (3a) was equally as potent as the formyl compound against HSV-1, but one-fifth as active against HSV-2, 100 times less effective against vaccinia, and 25 times less toxic for the host cells. In addition, compound 3a was about 10 times less active than 2a in inhibiting thymidylate synthetase in vivo (as reflected by a differential inhibition of dThd and dUrd incorporation into host cell DNA). The dithiolane (4a) did not exert an appreciable effect on either virus multiplication or dThd or dUrd incorporation, nor was it cytotoxic. All these compounds as their 5'-phosphate derivatives were potent in vitro inhibitors of thymidylate synthetase (Lactobacillus casei). The inhibition was competitive with substrate with Ki/Km ratios of 0.05 for the formyl 2b, 0.5 for the oxime 3b, and 0.2 for the dithiolane 4b. Thus, 3b was 10 times less active than 2b as an in vitro inhibitor of thymidylate synthetase, which appears to corroborate the in vivo findings.

Antiviral Agents↗
PubMed1980

Cell-mediated immunoprotection in blastomycosis.

Delayed hypersensitivity can be induced in C57BL/6J mice by two subcutaneous injections of Merthiolate-killed Blastomyces dermatitidis yeast cells in Freund incomplete adjuvant. Development of delayed hypersensitivity peaked at the day 18 post-primary antigen-emulsion injection, as determined by footpad sensitivity tests. Mice rendered hypersensitive to B. dermatitidis were protected from the lethal effect of a blastomyces infection. The protection effects were shown both in mortality tests and in data from organ cultures as expressed by indices of resistance. Data from this study show that there is a close parallel relationship between host resistance and the prevailing level of delayed hypersensitivity.

Animals↗